> -----Original Message----- > From: Tony Lindgren [mailto:tony@xxxxxxxxxxx] > Sent: Friday, January 09, 2009 6:27 PM > To: Shilimkar, Santosh > Cc: Pandita, Vikram; linux-omap@xxxxxxxxxxxxxxx > Subject: Re: [PATCH] [OMAPZOOM] OMAP : DMA: Spurious interrupt fix > > * Shilimkar, Santosh <santosh.shilimkar@xxxxxx> [090109 14:52]: > > > -----Original Message----- > > > From: Tony Lindgren [mailto:tony@xxxxxxxxxxx] > > > Sent: Friday, January 09, 2009 4:58 PM > > > To: Shilimkar, Santosh > > > Cc: Pandita, Vikram; linux-omap@xxxxxxxxxxxxxxx > > > Subject: Re: [PATCH] [OMAPZOOM] OMAP : DMA: Spurious interrupt fix > > > > > > * Shilimkar, Santosh <santosh.shilimkar@xxxxxx> [090109 12:51]: > > > > > > > > Tony, > > > > Regarding your proposal of doing the no. of channel > > > reservation during runtime has one problem. > > > > > > > > The whole idea was not to restrict users from using all 32 > > > channels and hence the config option. For OMAP secure chips, > > > few security drivers which will execute in secure contex > > > needs dedicated DMA channels and kernel dma library can't be > > > used in that case. So in such cases, required DMA channels > > > can be reserved using this config option. For GP devices all > > > 32 channels can be used currently. > > > > > > > > If it can done in better way, please suggest. > > > > > > Well how about passing the configuration for the DMA channels > > > from board-*.c file then? > > This is certainly a good option if the setting is fixed for > a particular board type. With this how do we ensure user > configurability. Lets say on a particular board, two > users/customers wants to use separate configurations for DMA > channels because of the needs what mentioned earlier. Then > again we need some kind of comfit option. > > Another clean way to achieve this is through 'bootargs'. > But this might be too much of a design for this requirement. > > Hmm, well how about starting with all of them, and allow > limiting the active DMA number via /sys? I guess we could > just set some of the DMA channels inactive that way. > > Or maybe allow setting indvidual DMA channels inactive > via /sys? This won't be a good option because of few limitations. - dma library init will configure the entire register set for all the channels. So through /sys disable , you have to mask all of this registers with appropriate mask depending on the no of channels deactivated. This is almost like doing another DMA init. - Secondly the security driver is active even before the dma library is initialed and hence it won't get the required reservation of channels which is bottleneck. - If both, dma library and security driver configure the DMA channels then, you end up in a problem because the way OMAP DMA hardware is. Just a brief - "In contrast to the SDMA.DMA4_CSRi registers, the SDMA.DMA4_IRQSTATUS_Lj registers are updated regardless of the corresponding bits in the SDMA.DMA4_IRQENABLE_Lj registers". For more details, you can refer the DMA section in TRM. Because of above, this is not seems to be an option. > > > > Time being if needed what best I can do is, to split this > > > patch into two parts as mentioned earlier. This will avoid > > > confusion of spurious interrupt issue and dam channel reservation > > > OK > > I will do this once I get some time for sure. > > Great! > > Tony Regards, Santosh -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
